Polyamides and their preparation



Patented Dec. 2, 1952 "POLYAMIDES AND THEIR PREPARATION Charles J. Albisetti, Jr., Wilmington, DeL, as-

signor to E. I. du Pont de Nemours & Company, Wilmington, DeL, a corporation of Delaware No Drawing.

Application March 13, 195.0,

Serial No. 149,453

14 Claims.

;.This..invention relates toinewgpolymericxmaterials and more particularly; to;new polyamides and to a'method for their preparation.

The condensation betweennitriles: and olefins in aqueous acidic media to form amides has been described (Ritter and Minieri,;J. :Am. Chem. .Soc. 70,- 4045 (1948) Extension of this reaction 'to the preparation of.:polyamides by the condensation of dinitrileswith ditertiary olefins has also. been :described. (copendingapplication-Ser.

No. 72,775, filed January 5,. 1949, by Magat). i :In View of the factsthat .delta-aminovaleric acidon heating gives no vpolyamide '-(U. "S. Patent 2,071,253);- but only delta-valerolactam (Schotten,

Ber. 21, 2240 (1888)), and thatid'elta-valero- =lactam itself has not "been polymerized iby methods (U. S. Patents" 2,241,322: and 2,251,519)

which convert its homolog,- epsiloncaprolactam,

.to" aripolyamide, it wasito be expected that the condensation of an olefinic nitrile'in'which. the double bond and the nitrile groups are separated by three carbon atoms should proceed to give exclusively-the cyclic..lactam. Surprisingly, it

has now; been found that: cyclic :lactams are not .produced, but that. polyamides are formed.

:It.-isan object of thistinvention :to: preparenew polymeric materials and to provide arnovel process for theirpreparation. .A'furtherobjectris to provide novelpolyamides and-a processfor their preparation by. condensation". of certain selected acyclic mono-unsaturated zmononitrilesnin- -which the carbon atom containing the. ethylenic double ,bond-andthe nitrile group are-separatedbythree carbon atoms. Other. obj ectswill appear hereinafter. 7

These objects are accomplished by the following invention, which comprises condensing in strong acidic media" an acylic mono-unsaturated mononitrile in which the unsaturation is ethy1- enlc and in the 5-position and which hasan alkyl or aralkyli'substituentin the'S-position. The novel products of .this invention are polyamides resulting- -from the self-condensationnof" atzleast two molecules of the abovevdefined Iv unsaturated nitriles. These products have-a [plurality-of amide groups and contain the structural unit:

(I) R an R-'o-H -t t t HALE i t t wherein. R represents a hydrogen atom or. an

"a1k'y1 groupandR" represents an alkyl or aralkyl group. The dimeric polyamides' resulting"from the condensation oftwo molecules of the unsaturated? nitriles"have .the' formula:

wherein. Ri representsrza hydrogen latoin or an alkyl group and-R, representsan alkyl or aralkyl group. Thepolymeric;polyamides resulting-from the condensation-.ofthree ortmorermolecules' of the unsaturated -..nitrile 1 contain,.-.a;.1plurality of structural :units '(the recurringstructural. unit) of "Formula I. .Especially-preferred embodiments of this invention .are-polyamides containing this structural unit in whichR'---is analkyloraralkyl group of not more than 7 carbon atoms, and pref erably is an alkylgroup of from. 1-.to 5 carbon atoms, and where -R :isrhydrogen-or anralkyl group of notx'more than:3.= carbonatoms;- and preferably hydrogen'or'methyl.

The unsaturated nitrilesrusedin the process of this invention have the generalformula:

R- R"R,.H:-R R t ces t t-s wherein R represents" a hydrogen atom o1" an alkyl group and Rrepresentsan alkyl or an aralkyl group. Preferred mononitriles for use in this invention have this general formula in: which R represents ahydrogen atom or an alkyl' group of not more than" 3 carbon atoms and preferably hydrogen or methyl and wherein It represents an alk'yl-pr aralkyl' groupof not more than? carbon atoms" and preferably an I alkyh group" of veniently prepared by contactingone mole of? an acyclic mono-unsaturated:mononitrile having at least seven carbon atomsyin Whichthaunsaturation is ethylenic and in the 5-position, 'andiwhich has an alkyl or aralkyl groupin. the 5-position, e. g., 5-methyl-5-hexenenitrile, with from three to four moles of strong sulfuric acid, e. g., sulfuric acid of 65 to 85% and preferably from 72 to 30% concentration, .at -a temperature. between 10 C.:and 30 C. andpreferablylat about 0"C.

The sulfuricdacid ..is..usual1y. aqueous acid of these concentrations, but it can be diluted with organic acids such as aceticacid instead of water. For example; a. mixture of 72%: 'HzSOr and: 28% glacial acetic acid. can be substituted for 72% aqueous sulfuric acid.

The unsaturated'nitrile can be added" to the sulfuric acid at the specified temperature, or if desired, the acid can be added to the nitrile. In either case it is essential that the rate of addition of one reactant to the other be controlled carefully so as to maintain the temperature of the resulting mixture within the above-specified range, since the reaction is exothermic. The actual rate of addition depends, of course, on the effectiveness of the cooling means employed. After the addition of reactants is finished, the reaction mixture is allowed to stand for a short time to complete the reaction. A period of time ranging from one-half to four or five hours is generally sumcient, although longer times, e. g., up to several days, are not harmful.

The resulting reaction mixture is poured into an excess of cold water or onto ice and any unreacted nitrile present separates as an insoluble oil which can be recovered by conventional means. The aqueous solution is made alkaline with an aqueous solution of an alkali metal hydroxide or carbonate, e. g. sodium or potassium hydroxide, or sodium carbonate, or with ammonia, and the organic material is isolated by extraction with an organic solvent such as chloroform or diethyl ether.

Aromatic hydrocarbons such as benzene are solvents for the dimer but they do not dissolve appreciable quantities of higher polymers. The organic solvent extract is dried by conventional means, e. g. by a desiccant such as anhydrous sodium sulfate, and the solvent removed by evaporation or distillation. The lower molecular weight polymers such as the dimers and trimers can be isolated by distillation and the higher polymers are left as non-volatile residues. When the reaction product is principally a solid polymer it can be separated directly from the reaction mixture after addition of an alkali metal carbonate without further isolation steps.

The invention is illustrated in further detail by the following examples in which the proportions of the ingredients are expressed in parts by weight unless otherwise noted.

Example 1 To a cold C.) stirred mixture of 206 parts of concentrated sulfuric acid (95.5% minimum H2804) and 88 parts of water is slowly added 66 parts of 5-"nethyl-5-hexenenitrile. After addition is complete the mixture is allowed to stand at room temperature for two days, then poured into 3000 parts of cold water and made alkaline with concentrated aqueous sodium hydroxide solution. The reaction mixture is extracted with chloroform, and the chloroform extract separated, dried over anhydrous sodium sulfate, and distilled. After removal of chloroform there are obtained 5-methyl-5-hexeneamide, a higher boiling viscous liquid, a solid which distills at 180-240 C./1 mm., and, as a non-volatile residue, a yellow. hard clear resin which is a polyamide having the recurring unit On repetition of this experiment there is ob-- tained '7 .0 parts of the distillable solid, which is the dimeric amide having the formula CH3 0 CH; 0 CHz=( 3-CH1CH2OH -NH;CHzCHCHz -NH This dimer boils at 185-200 C. at 0.15 mm., is

insoluble in water and reacts with potassium permanganate. It has a melting point of 126-l29 C. when recrystallized from ethyl acetate.

Anal. calcd for C14H26O2N22 C, 66.2%; H, 10.23%; N, 11.09%. Found: C, 66.0%; H, 10.32%; N, 11.19%.

The structure of this compound is confirmed by infrared spectra showing the presence of the following groups:

(H) 1 l?.\ R-CN-R 0:01;,

and

o R-(IJNHZ wherein R and R are alkyl groups.

Example II To a cold (0-2 C.) stirred mixture of 25 parts of glacial acetic acid and 27 parts of 5-methyl-5- hexenenitrile is added dropwise during four hours a mixture of 24.5 parts of water and 73.5 parts of concentrated (95.5% minimum H2304) sulfuric acid. After the addition of the sulfuric acid is completed, the mixture is held at a temperature of 2 C. overnight with stirring continued during the entire time. The resulting reaction mixture is poured onto 300 parts of ice and then neutralized with aqueous sodium carbonate solution whereupon a white sticky resin separates which is a polyamide having the recurring unit as set forth in Example I. After drying, this polyamide has a sticking point of 70 C. and melting point of about C. The polymer is soluble in hot ethanol, but is insoluble in benzene. It has a molecular weight of 860, determined by boiling point elevation in ethanol.

Anal. calcd for (CvHmONMc: N, Found: N, 11.11%.

Example III To a cold (2 C.) stirred mixture of 34 parts of concentrated sulfuric acid and 12 parts of water (aqueous sulfuric acid of 71% concentration) is slowly added 16.5 parts of S-methylene- 7,7dimethyloctanenitrile. After the addition is complete the mixture is allowed to stand for 2 hours and then poured into cold water and made alkaline with sodium carbonate. The reaction mixture is extracted with chloroform, and the chloroform extract separated, dried over anhydrous sodium sulfate, and distilled. In addition to recovered nitrile, there is obtained 4 parts of Example IV To a cold (5 C.) stirred mixture of 17 parts of concentrated (95.5% minimum HzSO4) sulfuric season's? has n,

acid-and6':partsbt watersis'lslowly-addedflfi parts of? 244:4;5=tetramethyl fiehexenenltrile :(prepared from tetramethylethylene and methacrylonitrile). After-'continuingthe reaction and working upithe reaction mixture .by the process of;

Example IIIfthere are obtained 2.5 parts of material boiling at 80-180 'C./0.'7 mm., 1.5 parts of dimeric amide, boiling at 180-210 C./0.7 mm., and as a nondistillable residue, 2.5 partsz-oha clear, yellow, solid polyamide having the recur-i1 ring unit (3H, on, cm i This polyamide when fused can be manually spun @130. aifiber.

Example V Fiveparts of 5-benzyl frehexenenitrile21s added;= :zz slowhtid 122. parts of 85%raqueous sulturl acid at held at this temperature for about 2 hours. The reaction-mixture is then poured onto ice and a" noncrystallizable solid separates out. This; polymer contains no 'unsatur'ationias evidenced by a negative permanganate test and has the recurring unit ually spun-to a? fiber.

Thegexamples have illustrated the polymers of this intention and their preparation by reference to the condensation-offour specific nitriles -g However, any acyclic monounsaturated mononitrile in which the unsaturation is ethylenic and is in the 5-position and which has an alkyl-or aralkyl substituent also in the 5-position can be employed in the process of this invention. Examples of z 'otherfi pperable.-- mononitriles include fi-ethyl-fi-hexenenitrile, 2,5-dimethyl-5-hexenenitril e,-' and 5-methylene-2,7,'7=trimethyloctane- 'nitrile. The polymers formed from these partic- ':,.;uiar::nitri-les have i the" 'followinge respectiveihim,,

mulas (in which n represents aipositiveiinte'ger greater than 1) 'In" addition to sulfuric acid,"other strong acids can be. used to polymerize acyclic monounsaturated n'iononitriles by the process of this invention. For example, formic acid, phosphoric acid and alkanesulfonic acids are useful for this purpose.

a6 IThe acyiclie xmonoethylenically unsaturated mononitriles: usedias'fstartingxmaterialsi for'ithe polymers offlthis invention can he -prepared by the thermal addition of an alpha, beta-ethylenically unsaturated *mononitrile' to a neutral olefinic compound free of non-conjugated unsaturation having an acyclic .olefinic double bond and having adjacent to one of the doubly bonded carbons a carbon atom having attached thereto at-=-1easta one A 1 hydrogen atom. This process is describedi' indetail in U.':-S: "patent application,

Serial No. 10I-;9'05,' filed June '28; l949} by"-C= J. Albisetti and'N G. Fisher, now abandoned, or which application Ser. No. 168,387, filed June 15, 1950, is acontinuation.

The polymers of this invention have a wide range :of molecular weights: and? area useful in many: differentmpp ications. :The lower. molecular weightpolymers, lie. the dimers and t1imers, 0 are useful as nonvolatile plasticizers and modifiers for natural and synthetic resins. The higher molecular wei'ghtpolymers are useful in the formation of fibers and coating compositions and as textile treating agents.

As many apparently widely different embodiments of this invention may be: made without departing from the spirit and scope thereof, it is to be understood that this invention is not limited =ito 'the specificaiembo'diments vthereof except as adefine'd in? the appended rlaims.

I claim:

1. A polyamide containing aplurality of struc-- tural units? and as the sole. recurring unit, the structural unit having the formula:

wherein R is selected from the, group consisting of alkyl of? not more than 3 carbon atoms and hydrogen and'R is selected from'the group con sisting of alkyl and aralkyl.

2. A polyamide containing a plurality ofstrucltu-ral uni-ts: and'- asthe so1e recurring unitnth structural unit having :the formula:

"-R R 11 0 is, lion-let's H R 1'1 it 1'1 {wherein R is methyl and R "is 'arr falkyl group of from 1 to 5 carbon atoms.

3. A polyamidecontaining a 'plur'ality of structural units and as the solerecurringiunit the "structural v unit: having thef formula:

wherein R1is-methyl and9Rf is-an' 'aralkyl group.

4. A polyamide containing aplur'ality of structural units and as the sole recurring unit, the structurarunit having the formula:

5. A polyarnide containing a pluralityof structural units and as the sole recurring unit, the structural unit having the formula:

(1 1112 LHaC(l]CHa J 6. A polyamide containing a plurality of structural units and as the sole recurring unit, the structural unit having the formula:

| CH3 CH3 CH3 7. A polyamide Containing a plurality of structural units and as the sole recurring unit, the structural unit having the formula:

8. A polyamide containing a plurality of structural units and a the sole recurring unit, the structural unit having the formula:

wherein R is an alkyl group of from 1 to 5 carbon atoms.

9. A polyamide containing a plurality of structural units and as the sole recurring unit, the structural unit having the formula:

wherein R is an aralkyl group.

10. A polyamide having a plurality of amide groups and consisting of the structural units and wherein R is alkyl and the first structural unit is a terminal structural unit.

11. A polyamide having a plurality of amide groups and consisting of the structural units wherein R is aralkyl and the first structural unit is a terminal structural unit.

and

12. A polyamide having a plurality of amide groups and consisting of the structural units wherein R is alkyl of not more than 3 carbon atoms and R is alkyl and the first structural unit is a terminal structural unit.

13. A polyamide having a plurality of amide groups and consisting of the structural units wherein R-is alkyl of not more than 3 carbon atoms and. R, is aralkyl and'the first structural unit is a terminal structural uni-t.

14. A polyamide having a plurality of amide groups and consisting of the structural units structural unit.

CHARLES J. ALBISETTI, JR.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,130,948 Carothers Sept. 20, 1938 2,162,971 Ralston June 20, 1939 2,293,388 Hanford Aug. 18, 1942 2,356,516 Hagedorn Aug. 22, 1944 2,573,673

Ritter Oct. 30, 1951 

1. A POLYAMIDE CONTAINING A PLURALITY OF STRUCTURAL UNITS AND AS THE SOLE RECURRING UNIT, THE STRUCTURAL UNIT HAVING THE FORMULA: 